There are many disadvantages to the old selection criteria. The most obvious is that it does not mention the type of hydrophobic equipment and the hydrophobic method. The selected trap often does not match the actual load. What is particularly serious is that the thermodynamic disc trap (foundation of the old selection standard) was mistakenly thought to be a universal trap by people, especially in the workshop.
As early as 1980, the Grangemouth plant began to monitor the performance of steam traps because the maintenance engineers complained about the short life of steam traps. Two years later, the Huddersfield factory also performed the same monitoring.
During the monitoring, the traps were first investigated to understand the types of existing traps and to check the load during the selection. At the same time, related tests were also conducted. The initial results were surprising. The results of tests performed on a 415 steam trap in a workshop showed that 19% of the traps were effective and 63% of the load was not matched.
An inspection of 132 steam traps on the steam supervisor showed that 42% of the traps were effective. The inspection of the life of the trap also began in 1980 and continues to this day.
To test the energy savings of various traps, fresh steam loss tests were performed on traps being used in the two manufacturers' laboratories. The test is carried out in the laboratory, ie 20°C, still air. This experiment did not detect the heat loss of the trap body. The load of condensate in the test is a common 10-20 kg/hr (22-44 lbs/hr). As the most widely used thermal power disk trap, it has the lowest energy-saving effect, and its service life is extremely short compared to inverted bucket steam traps.
In situations where the heat requirement is not high, replacing the thermodynamic disc trap with a thermostatic trap will increase the energy savings and at the same time ensure the service life.
These experiments also revealed that mechanical traps (ie, inverted buckets and float traps) ensure that the steam is free of condensate, regardless of whether the condensate load is large or the load is small. The thermostatic trap increases the load. It is easy to accumulate condensate. In addition, bimetal traps tend to be unstable.
The new "Guidance" after the change includes a trap selection table.
The current selection recommendation:
Inverted bucket trap:
As the first choice for all process loads and steam mainline traps, where all steam needs to be hydrophobic.
Float Thermostatic Steam Traps:
Used for process hydrophobicity, especially in applications where the control load is less than 3.5 kg (50 psig) or where the air content is high and there is a problem with the installation of an inverted bucket trap.
Balanced pressure trap:
Used as an insignificant heating or heating system.
Bimetal thermostatic trap:
It is used for the low-temperature or frost-proof conditions of heating lines or heating systems. This type of trap can maximize the use of sensible heat in the condensate or prevent product overheating. Its valve body is all stainless steel.
Thermal power disk traps:
As long as the previous experience proves its good performance, it can be used as an alternative to inverted bucket traps, limited use on steam mains and heat pipes under 17 kg in pressure, or as a product replacement for higher steam pressure. Due to its low energy efficiency and short service life, it is not recommended.
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